Tas: Should the Southern Ocean get an iron supplement?

AAP General News (Australia)
12-13-2001
Tas: Should the Southern Ocean get an iron supplement?

By Don Woolford

HOBART, Dec 13 AAP - Scientific debate over whether the Southern Ocean should get an
iron supplement to help it absorb carbon dioxide (CO2) has been sparked by Australia's
most ambitious Antarctic expedition to study climate change.

Some scientists believe that seeding the vast and icy ocean with iron is a feasible
way to curb global warming, while others regard it as a "rubbish" solution.

The expedition, which studied the Southern Ocean from near Hobart to Commonwealth Bay
in Australian Antarctic territory, ended today with the return of the icebreaker Aurora
Australis.

The ship carried 70 scientists from 11 countries - an unprecedented mix of physicists,
chemists and biologists - to gather data on how the ocean influences the world's climate
and the global carbon cycle.

While the information will take about two years to fully analyse, the voyage confirmed
earlier evidence that iron, a key nutrient for phytoplankton, or single-celled plants,
was scarce in both surface waters and sea ice.

CSIRO oceanographer and chief scientist on board Steve Rintoul said the Southern Ocean
absorbed about 25 per cent of the CO2 in the world's atmosphere and marine plants were
a critical part of the process.

Dr Rintoul said there was now evidence that while the ocean had plenty of other nutrients,
the lack of iron was limiting plant growth.

Voyage leader and chief biologist Harvey Marchant said some scientists believed it
was sensible and feasible to boost plant growth through giving the ocean iron supplements.

But other scientists said it was rubbish - a technological fix to a man-made problem.

Dr Marchant said the problem was that supplementing the natural iron might stimulate
the wrong plants - ones of little value to either CO2 absorption or grazing animals.

He said more work was needed to try to pinpoint the right place and time of the year
when extra iron would be helpful.

Ocean plants suffering iron deficiency were only part of the climate change jigsaw
studied during the expedition.

Dr Rintoul said computer modelling suggested the ocean was taking up less CO2 because
of less biological activity and because the currents that took water from the surface
to the depths were lessening.

With humans adding ever more CO2 to the atmosphere and the ocean absorbing ever less
of it, the double whammy effect had big implications for global warming.

"But we don't know how reliable the modelling is until it's tested through observations
from the real ocean," Dr Rintoul said.

His expedition was a major part of this process.

It will be followed up by three Japanese-led expeditions during the next four months,
which will give the scientists unbroken data from spring to autumn.

AAP dw/las/br

KEYWORD: ANTARCTIC CARBON

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